An agricultural seeding machine such as a row crop planter or grain drill places seeds at a desired depth within a plurality of parallel seed trenches formed in soil. In the case of a row crop planter, a plurality of row crop units are typically ground driven using wheels, shafts, sprockets, transfer cases, chains and the like. Each row crop has a frame which is movably coupled with a tool bar. The frame may carry a main seed hopper, herbicide hopper and insecticide hopper. If a herbicide and insecticide are used, the metering mechanisms associated with dispensing the granular product into the seed trench are relatively simple. On the other hand, the mechanisms necessary to properly meter the seeds, dispense the seeds at predetermined relative locations within the seed trench are relatively complicated.
The mechanisms associated with metering and placing the seeds generally can be divided into a seed metering system and a seed placement system which are in series communication with each other. The seed metering system receives the seeds in a bulk manner from the seed hopper carried by the frame. Different types of seed metering systems may be used, such as seed plates, finger plates and seed disks. In the case of a seed disk metering system a seed disk is formed with a plurality of seed cells spaced about the periphery of the disk. Seeds are moved into the seed cells with one or more seeds in each seed cell depending upon the size and configuration of the seed cell. A vacuum or positive pressure air differential may be used in conjunction with the seed disk to assist in movement of the seeds into the seed cell. The seeds are singulated and discharged at a predetermined rate to the seed placement system.
The seed placement system may be categorized as a gravity drop system or a power drop system. In the case of the gravity drop system, a seed tube has an inlet end which is positioned below the seed metering system. The singulated seeds from the seed metering system merely drop into the seed tube and fall via gravitational force from a discharge end thereof into the seed trench. Further, the rearward curvature reduces bouncing of the seed as it strikes the bottom of the seed trench.
A seed placement system of the power drop variety generally can be classified as a seed conveyer belt drop, rotary valve drop, chain drop or air drop. These types of seed placement systems provide more consistent placement of the seeds along a predetermined path at a desired spacing.
Certain seed types, notably flat corn seed with insecticide or other treatments, are difficult for vacuum meters to singulate. Pour singulation of difficult seed types is characterized by doubles, skips and bunches of seed carried by the disks. Doubles and skips refer to multiple seeds and no seed respectively in each seed cell. Bunches are multiple seeds carried up by the seed pool accelerators which protrude from the surface of the seed disk. These seed types generally are best planted with a flat seed disk or in combination with a double eliminator. Compared to a celled disk, a flat disk has less favorable seed trajectory into the seed tube, generally requires more vacuum and a production double eliminator, adjustment is difficult.
The double eliminator or singulator generally does an adequate job of ensuring that a single seed is retained within the seed cell and carried by the metering disk to the point where it is dropped into the seed placement system. The seed cell typically consists of an opening or hole through the disk and the pressure differential maintained across the disk holds the seed within the cell. Because of the irregularity of naturally occurring seeds, it is possible for a seed to be stuck into the hole, and therefore prevented from dropping off at the assigned time and location to the seed placement system. Furthermore, it is possible for seeds to split and be placed against the metering disk in a size smaller than normal. This tube may cause the partial seed to be wedged in the hole and resistant to dropping at the assigned location.
What is needed in the art is an agricultural seeding machine having a seed disk that is resistant to seeds being lodged within the holes in the seed disk.